1. Field of the Invention
The present invention relates in general to the mechanism for supplying power to electronic devices, and more particularly, but not exclusively, to a fully electromechanical automatic transfer switch having a mechanism for accommodating brownout conditions.
2. Description of the Related Art
Transfer switches allow switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems. Transfer switches may be seen where emergency power generators are used to provide back up power from the utility source. The transfer switch allows switching from utility power to emergency generator power. The switch is a manual switch, an automatic switch, or a combination of both. During a power outage, transfer switches isolate the emergency circuits from the utility line, allowing for efficient operation of the generator without backfeeding into the utility. An automatic transfer switch (ATS) is a type of transfer switch that automatically connects one of two alternating current (AC) line sources to an electrical load, usually the better of the two sources.
In virtually every power setting, “brownouts,” or conditions where lower voltage than normal is supplied to the load, may present themselves. ATS devices generally use microcontroller-based “smart” electronic control circuits to accommodate this condition. Supporting the microcontroller, however, requires voltage sensors, signal condition equipment, power supplies, coil drive circuitry, and control firmware. These additional requirements add to system cost and complexity, and present several potential points of failure.